Meltable plastic spacer for securing coil to tubular support and housing, and methodof assembly



3,138,771 TUBULAR OF ASSEMBLY 1958 June 1964 B. M. GOLDSMITH ETALMELTABLE PLASTIC SPACER FOR SECURING COIL TO SUPPORT AND HOUSING, ANDMETHOD Original Filed Feb. 19,

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United States Patent 3,138,771 MELTABLE PLASTIC SPACER FOR SECURING COILT0 TUBULAR SUPPORT AND HOUSING, AND METHOD OF ASSEMBLY V 7 Bernard M.Goldsmith, Little Silver, N.J., and Walter T.

Sutton, .Ir., Lexington, Ky., assignors, by mesne assignments,toNytronics, Inc, Phillipshurg, N.J., a corporation of New JerseyContinuation of application Ser. No. 716,106, Feb. 19, 1958. Thisapplication Dec. 12, 1961, Ser. No. 162,623 3 Claims. (Cl. 336*92) Ourinvention relates to an improved electrical coil and transformerconstruction rendering the same particularly useful in the automaticassembly of such circuit components into circuits, as into printedcircuits. This application discloses improvements over and modificationsof the various forms disclosed in copending Goldsmith application Ser.No; 626,175, filed December' t, 1956, now Patent No. 2,836,805. Thepresent application is a continuation' of my copending application Ser.No. 716,106, filed February 19, 1958.

It is an object of the invention to provide an improved construction ofthe character indicated.

It is another object to provide an improved electricalcoil circuitelement which can be fabricated at substantially reduced cost.

It is a specific object to achieve the above objects with a constructionin which the ends of the wire of the coil or coils are themselves themounting prongs, of strength adequate to provide the substantialmounting support for the circuit element.

It is in general an object to meet the above objects with an extremelyrugged and simple device which can achieve or exceed the electricalperformance of previous structures, and which may be so rugged andpermanent as to constitute a trouble-free component for the life of thecircuit in which it is embodied.

Other objects and various further features of novelty and invention willbe pointed out or will occur to those skilled in the art from a readingof the following specification, in conjunction with the accompanyingdrawings. In said drawings, which show, for illustrative purposes only,preferred forms of the invention;

FIG. 1 is a longitudinal sectional view (taken along the line 1-1 ofFIG. 3) of a coil construction embodying features of our invention andjust prior to a final assembly step;

FIG. 2 is a view similar to FIG. 1, but illustrating completion of thefinal step;

FIG. 3 is a bottom-end view of the structure of FIGS. 1 and 2;

FIG. 4 is a view similar to FIG. 1 to illustrate a modification;

FIG. 5 is a view in perspective to illustrate an element of FIG. 4; and

FIG. 6 is a fragmentary longitudinal sectional view to illustrate afurther modification.

Briefly stated, our invention contemplates application to theconstruction of coils, transformers, chokes and the like for use inelectronic circuit assemblies, as for example, in the video amplifier ofa television set. The construction features integral formation of theturns of the electrical coil with the mounting leads or prongs and, forthis purpose, employs relatively heavy and stiff wire for the turns ofthe coil or coils. The assembly is made rugged and adaptable to receivean adjustably positioned magnetic core by securing the same with aplastic bonding agent, such as an epoxy resin.

The particular feature of the present invention is the employment of aninitially solid fusible member assembled with the coil and its housingand in adjacency with 3,138,771 Patented June 23, 1964 the coil, thesaid member having a melting point substantially lower than the meltingpoint of the housing, so that upon the passage of a heating current ofsufiicient intensity through the turns of the winding after initial assembly, the fusible member may be melted and allowed to flow intobonding relationship with the turns of the winding and the housing,thereby completing the permanent nature of the assembly.

In one form to be described, the fusible member serves as an axialspacing member for precisely determining the extent to which a givenwinding will be inserted upon initial assembly into its housing. In theother form to be described, the fusible member is a ribbon of suitablematerial interleaved with the turns of the winding. In both cases, thefusible member is in direct contact with the winding so that permanentbonding maybe achieved merely by heating the winding after assembly.

Referring to FIGS. 1, 2 and 3 of the drawings, our invention is shown inapplication to a coil assembly in which the coil 10 is developed orreceived upon, and concentrically supported by, a tubular coil-formportion or stem 11 of a plastic body member 12; it will be appreciatedthat concentric support, as used here, contemplates substantialcoincidence of the axes of the coil and ,of the coil-form. The bodymember 12 may be generally cupshaped and, in addition to the tubularmember 11, may include an outer tubular member 13, joined at the upperend, as'at 14, to the inner tubular member 11, so as to define therewithan annular space 15 open at the lower end to receive insertion ofthe'winding 10.

The winding 10 is developed from relatively heavy and stiff insulatingwire and is shown as a single layer of turns, the ends of which are soformed and trimmed as to project axially beyond the axial confines ofthe coil and so as to project axially beyond the open end of the housing12 when assembled thereto. Heavy plastic-coated copper magnet wire orCopperweld (coppersheathed steel wire) is well adapted to form thewinding means 10.

The wire from which the winding 10 is formed is preferably so ruggedthat the projecting ends 16-17 of the coil 10 may serve as the mountingpins for the finished structure, so that no soldering or otherconnection to separate mounting pins is necessary to integrate thecircuit component into its ultimate chassis. For convenience inmounting, the leads 1617 may be nail-pointed by employing conventionalmachinery, but we indicate our preference that the projecting ends 16-17shall be merely dipped in a pool of solderand slowly raised so as todevelop pointed solder ends 16'17 in the manner of a .stalactite, thesolder being further desirable for ultimate simpler permanent assemblyinto a printed circuit. The leads 161 7 may project for different axiallengths, thereby p'rovidingunambiguous terminal identification.

Various means may be employed to close the open end' .of the containeronce the winding 10 has been assembled therein, and in the form shown weemploy the means described in greater detail in Goldsmith applicationSerial No. 715,377, filed February 14, 1958. The closure means may thuscomprise a separate cover 18 of plastic material which may be formed ofthe same kind of material as thehousing 12; the cover 18 is with aplurality of angularly spaced openings 21-222324, and two of theseopenings 22-24 are employed to locate the axially projecting integralends 16-17 of the winding 10. The cover 18 is preferably so designed asto fit with a forcefit within the outwardly flared end of the slightlytapered outer tubular member 13 of the body 12. The closure member 18also has a central opening through which the stem 11 of the housing 12projects, and the outwardly projecting ends may be formed over, as byspinning, to define a b ead 19 for retaining the parts in permanentlyassembled relation.

the inner end of the outer winding 26.

In accordance with the invention, precise preliminary assembly isachieved by first inserting a spacer abutment member or pellet 20 ofannular shape over the central tubular housing part or stem 11 and bythen applying the winding in direct axial abutment therewith, the spacermember 20 being so devised'as to define the exact desired abutment planefor the inner end of the winding 10. Upon thereafter securing the cover18 by means of the bead 19, precise and accurate location of the winding10 on the stem 11 is achieved, and for many purposes, the assembly maybe considered complete.

In accordance with a preferred employment of the invention, the spacerabutment member or ring 20 is made of a plastic material having asubstantially lower melting point than that of the housing 12. Themelting point should be such that normal operating temperatures of thecoil 16 will not be anywhere near adequate to soften the material ofmember 20, but so that, upon heating for assembly purposes to atemperature elevated with respect to normal operating temperature, themember 20 may be caused to melt. Thus, once the parts have beenassembled preliminarily into the relationship shown in FIG. 1, a currentof sufficient intensity is passed through the winding by establishingconnections at 16-17, and the material of spacer 20 is caused to flow.If the assembly is oriented with the closed end or cover 18 facingdownwardly, then the flow of plastic material will fill the intersticesbetween winding turns and the coil form or stem 11, and will assume afinal relationship within the housing as suggested at 25 in FIG. 2, thuspermanently bonding the winding turns to the coil stem and to the cover18. It is not necessary to achieve a bonding to the inner wall of theouter tubular portion 13 of the housing, but if this occurs, no harm isdone, the assembly being thereby made that much more rugged.

In the arrangement of FIG. 4, we illustrate employment of the principlesdiscussed in connection with FIGS. 1, 2 and 3 for the accommodation ofparts of a transformer, the principal dilference between FIGS. 1 and 4being the showing of a second winding 26 which may be of generally thesame nature as the winding 10, except for being wound on a slightlylarger diameter so as to derive concentric support from the periphery ofthe winding 10. As with the case of the winding 10, the ends of thewinding 26 may be bent axially out the open end of the container forlocation in the remaining openings 21-23 of the cover 18 and forprojection therebeyond. The said wire ends for the second coil 26 aresuggested at 2728 in FIGS. 3 and 4.

In accordance with a further feature of the invention, the automaticassembly of a transformer such as that shown in FIG. 4 is facilitatedand made more precise by so contouring the end of the spacer pellet 20'that unique, positive, direct locating abutment is achieved for bothwindings 10-26 of the assembly. In the case of FIG. 4, it is assumedthat the outer winding 26 has fewer turns than the inner winding 10, andthat the axially inner end of the winding 10 shall extend furtherinwardly into the housing 12 than does the corresponding axially innerend of the outer winding 26. In the form shown, the spacer pellet 20'includes an additional projecting element 29 extending axially beyondthe main body of the spacer pellet 20' so as to determine a positivelimit for Thus, upon preliminary assembly, the parts may be axiallyabutted in the relation shown in FIG. 4, and the housing may be securedby beading the stem at 19 into retaining relation with the cover 18.Upon subsequently heating one or both of the windings 111-26, thematerial of the fusible spacer pellet 2th will commence to flow, sothat. on cooling, a bonded relationship is established for the turns ofthe two windings to each other and to the stem 11, as well as tothecover 18, and perhaps also to certain parts of the skirt or outertubular part 13 of the housing 12.

In the arrangement of FIG. 6, the parts may be preliminarily assembledin the manner discussed in said Goldsmith application Ser. No. 715,377,or they may be assembled against a non-fusible spacer pellet or shoulder(not shown, but similar to that shown at 20 in FIG. 1). The principaldifference between the embodiment of FIG. 6 and those of FIGS. 1 and 4is that the fusible material employed for plastic bonding is a ribbon 30helically developed in interleaved relation with the turns of thewinding 10 or 26, as the case may be. This will mean a slight spacingbetween successive turns of the winding 10 or 26, but once the partshave been assembled and a heating current passed through the turns ofthe winding, the ribbon 30 will melt; thus, on cooling, bonding to thecoil form or stem 11 will be secure and permanent, so that electricalcharacteristics will be permanently retained.

As indicated, it makes no difference whether the plastic ribbon isinterleaved with the primary or secondary turns in the case of atransformer, but in FIG. 6, I suggest the employment of the bondingribbon 30 merely for the inner winding, namely the winding 10; in FIG.6, turns for the outer winding 26 are suggested in phantom outline. Ineither case, heating current passed through the winding carrying thebonding ribbon 30 will be sufficient to achieve bonding of the turns ofboth windings to each other and to the stem 11.

It will be seen that we have described a relatively simple yet efiicientcoil construction lending itself to automated fabrication and toautomated later assembly into a circuit sub-assembly, as into a printedcircuit, the key means 31 being such as to facilitate unambiguouslocation in such assembly. In all cases, the lead wires are adequate tosupport the entire structure, even for automatic circuit-assemblyhandling, and yet they are integral with the turns of the coil or coils.

While we have described the invention in detail for the preferred formsshown, it will be understood that modifications may be made within thescope of the invention as described in the claims which follow.

We claim:

1. In combination, a plastic cup-shaped housing comprising inner andouter tubular portions joined at one end to define an elongated annularspace open to the other end, an electrical winding comprising aplurality of turns of relatively heavy and still wire of axial extentless than the axial extent of said annular space and supported by andderiving concentric support directly from one of said tubular portions,a ring-shaped spacer pellet of plastic material substantially coaxialwith the housing axis and having a melting point substantially less thanthat of said housing and received within said space in axially abuttingrelation with the closed end of said housing and in axially abuttingrelation with the adjacent end of said winding, whereby a positiveinitial axial location may be developed for axially assembling saidwinding within said annular space, and whereby, upon such initialassembly, and upon the passage of a heating current through saidWinding, bonding material may be available from said spacer pellet topermanently bond the turns of said winding to said housing.

2. In combination, a plastic cup-shaped housing comprising inner andouter tubular portions joined at one end to define an elongated annularspace open to the other end, an electrical winding comprising aplurality of turns of relatively heavy and still? wire of axial extentless than the axial extent of said annular space and supported by andderiving concentric support directly from one of said tubular portions,a ring-shaped spacer pellet of plastic material substantially coaxialwith the housing axis and having a melting point substantially less thanthat of said housing and received within said space in axially abuttingrelation with the closed end of said housing and in axially abuttingrelation with the adjacent end of said winding, a second electricalWinding comprising a plurality of turns of relatively heavy and stiffwire supported by and deriving concentric support directly from saidfirst winding, said spacer pellet being formed at the radius of turns ofsaid second winding with an axially projecting portion extending beyondthe location of pellet abutment with said first winding and in axiallylocating relation with the adjacent end of said second winding; wherebydesired initial axially located relations between both windings and thehousing may be developed, and whereby upon passage of the heatingcurrent through one of said windings, said windings may be bonded toeach other and to said housing in the desired relationship.

3. The method of permanently assembling an electrical coil of relativelyheavy and stiff wire to a tubular plastic coil form having an integralannular radially outwardly extending flange part at one end, whichcomprises the steps of preforming said wire into an axially extendingplurality of turns of substantially the outer diameter of said coilform, the ends of said wire being formed straight and projecting axiallybeyond the same single end of said turns and in angularly spacedrelation, assembling a 20 spacer washer of thermoplastic bondingmaterial over said coil form and in axially abutting relation with saidflange, assembling said coil to said coil form in axially abuttingrelation with said washer, whereby the axial location of said coil withrespect to said flange is uniquely and accurately defined, passing asufiicient electric current through said coil to locally melt at least apart of said thermoplastic bonding material, and removing said currentto allow cooling to thereby bond a part of said coil to a part of saidcoil form.

References Cited in the file of this patent UNITED STATES PATENTS812,657 Kitsee Feb. 13, 1906 2,455,136 Obert May 30, 1948 2,695,856Firth Nov. 30, 1954 2,836,805 Goldsmith May 27, 1958 2,941,172 SuttonJune 14, 1960 3,014,190 Sutton Dec. 19, 1961 3,024,433 Goldsmith Mar. 6,1962

2. IN COMBINATION, A PLASTIC CUP-SHAPED HOUSING COMPRISING INNER ANDOUTER TUBULAR PORTIONS JOINED AT ONE END TO DEFINE AN ELONGATED ANNULARSPACE OPEN TO THE OTHER END, AN ELECTRICAL WINDING COMPRISING APLURALITY OF TURNS OF RELATIVELY HEAVY AND STIFF WIRE OF AXIAL EXTENTLESS THAN THE AXIAL EXTENT OF SAID ANNULAR SPACE AND SUPPORTED BY ANDDERIVING CONCENTRIC SUPPORT DIRECTLY FROM ONE OF SAID TUBULAR PORTIONS,A RING-SHAPED SPACER PELLET OF PLASTIC MATERIAL SUBSTANTIALLY COAXIALWITH THE HOUSING AXIS AND HAVING A MELTING POINT SUBSTANTIALLY LESS THANTHAT OF SAID HOUSING AND RECEIVED WITHIN SAID SPACE IN AXIALLY ABUTTINGRELATION WITH THE CLOSED END OF SAID HOUSING AND IN AXIALLY ABUTTINGRELATION WITH THE ADJACENT END OF SAID WINDING, A SECOND ELECTRICALWINDING COMPRISING A PLURALITY OF TURNS OF RELATIVELY HEAVY AND STIFFWIRE SUPPORTED BY AND DERIVING CONCENTRIC SUPPORT DIRECTLY FROM SAIDFIRST WINDING, SAID SPACER PELLET BEING FORMED AT THE RADIUS OF TURNS OFSAID SECOND WINDING WITH AN AXIALLY PROJECTING PORTION